Could Creatine Supplementation Increase Cancer Metastasis? What Did the New Study Show?

What is creatine, and why is it used so widely?

Creatine is a natural compound that can be produced from amino acids in the liver, kidneys and pancreas, and can also be obtained from meat and fish. In tissues with rapidly changing energy needs, such as muscle and brain, it contributes to rapid ATP regeneration through the phosphocreatine system. The most extensively studied supplement form is creatine monohydrate.

When used with resistance exercise, it may provide small but measurable increases in strength, training capacity and lean body mass. A commonly used maintenance dose in general athletic use is 3-5 g/gün. Some programs use "loading" of approximately 20 g/gün for the first 5-7 days; however, loading is not essential to fill muscle stores. This distinction matters when interpreting the new study: the human experiment used, for 14 days, 20 g/gün, a loading dose approaching four to seven times the usual maintenance dose.

The absence of strong evidence that recommended doses cause kidney injury in healthy individuals does not automatically establish creatine's safety from an oncology perspective . General toxicity, kidney safety, performance benefits and tumor biology are different research questions.

How was the new study designed?

The paper by Sisi Xie and colleagues is not a single human clinical trial; it combines cell culture, genetically modified mice, different cancer models, molecular analyses and a small healthy-volunteer pilot into a translational research package. The study's strength is testing the same hypothesis through many experiments. Its most important limitation is not measuring cancer outcomes in humans.

In most mouse experiments, administering tumor cells through the tail vein bypasses early steps of metastasis, such as leaving the primary tumor and entering the circulation. These models are useful particularly for studying survival of tumor cells in the bloodstream and their establishment in the lungs; however, they do not fully reproduce the natural development of cancer in a person.

Proposed mechanism: the chain from creatine to metastasis

According to the researchers' findings, rather than directly stimulating mature platelets, creatine affects megakaryocytes , the bone marrow cells that produce platelets. Changes in the metabolic program of megakaryocytes make the next generation of platelets easier to activate.

The role of platelets in metastasis is not new. They can surround circulating tumor cells, protect them from mechanical stress in the bloodstream and immune surveillance, and facilitate attachment to vessel walls and exit into distant organs. What is new is the finding that a dietary metabolite can change platelet behavior through megakaryocytes , explained by the detailed CKB-STAT5B mechanism.

What was found in mice?

• In mice given creatine, the number or burden of lung metastases increased in different tumor models.
• Survival shortened in the melanoma model with spontaneous metastasis.
• Transferring platelets from creatine-treated mice to untreated mice also increased metastasis. This finding suggested that the effect was not limited to direct action on tumor cells.
• Reducing the creatine transporter in tumor cells did not completely eliminate the effect; however, in megakaryocytes, when Slc6a8 or Stat5b was inactivated, platelet activation and the increase in metastasis were prevented.
• A STAT5 inhibitor suppressed the increase in metastasis in mice.

These "gain and loss" experiments are stronger than a simple correlation. In other words, the researchers did not merely observe creatine and metastasis increasing together; they showed that the effect also disappeared when they blocked the proposed biological pathway. However, this does not establish that a STAT5 inhibitor can be used for this purpose in humans.

What was actually shown in 11 healthy volunteers?

In volunteers, circulating creatine rose above 150 µM from day 3 and remained around this level. Platelet count did not change. However, on day 14, platelet aggregation and adhesion measurements in response to some stimuli showed increases or trends toward increases. The response was not the same in every test: some measurements increased significantly with collagen and epinephrine, while not all results were significant with ADP and arachidonic acid. This heterogeneity does not support an interpretation that "all platelet functions increased dramatically".

Gene expression in circulating CD41-positive cells was investigated in four volunteers; increases in the platelet receptors GP6 and P2RY12 were reported. The volunteers' platelets before and after creatine were then administered with mouse melanoma cells to immunosuppressed mice. Human platelets obtained after creatine were associated with more lung metastases in mice.

Where is the study's evidence strong, and where is it weak?

Why does it still matter?

Taking a safety signal seriously clinically does not always require waiting until harm has first been seen in thousands of people. If the mechanism is strong, exposure is widespread and the possible outcome matters, the research agenda may change. This paper shows that, beyond creatine's sports performance and kidney safety aspects, its oncological safety should be investigated prospectively .

Why can it not immediately become a clinical verdict?

1. The human sample is very small: 11 people are insufficient for reliable subgroup analysis or analysis of rare harms.
2. Participants were not cancer patients: The metabolism of healthy people aged 20-25 differs from that of older cancer patients receiving treatment.
3. There was no control arm: Each participant was compared with their own baseline; effects of time, diet and measurement variables cannot be fully excluded.
4. The dose was high: 20 g/gün does not directly answer the question about the effects of a typical 3-5 g/gün maintenance dose.
5. No clinical event was measured: Platelet laboratory tests do not replace actual thrombosis or cancer recurrence.
6. Mouse models are artificial: Intravenous administration of tumor cells bypasses some steps in the metastatic chain.
7. Follow-up was very short: Cancer recurrence and metastasis can develop over months to years.

What had previous cancer studies shown about creatine?

Creatine's biology in cancer does not operate in only one direction. Some experimental studies reported support for CD8 T-cell energy capacity and antitumor immunity, while other models reported facilitated tumor cell movement and colonization. A 2021 study suggested that creatine could increase colorectal and breast cancer metastasis through SMAD2/3. The new study adds a second pathway to the same concern, independent of tumor cells, namely the megakaryocyte–platelet axis .

In humans, evidence is limited and mainly focused on the potential to reduce muscle loss:

ASCO's cancer cachexia guideline and ESPEN's clinical nutrition approach in cancer emphasize nutritional assessment, adequate energy and protein intake, symptom control and resistance exercise when possible. Creatine is not a standard cachexia treatment recommended for all cancer patients. The value of exercise in cancer care is not negated by this study; exercise and rehabilitation are not the same as the safety of a performance-enhancing supplement.

How should it be positioned for cancer patients today?

Practical assessment when a patient uses creatine

We previously emphasized that cancer patients' nutritional, rehabilitation and psychosocial problems should be integral to treatment in our article assessing cancer treatment in Türkiye . The conclusion here is not to ignore muscle loss, but not to replace evidence-based nutrition and exercise care with a supplement whose benefit is unproven or safety uncertain.

What research is needed after this study?

• Dose–response studies: Do a 3-5 g/gün maintenance dose and 20 g/gün loading produce the same platelet effect?
• Placebo-controlled human experiments: Platelet aggregation, activation markers and thrombin generation should be confirmed in independent groups.
• Cancer patient cohorts: Active cancer, post-treatment survival and different tumor biologies should be investigated separately.
• Clinical endpoints: Not only laboratory tests, but venous thromboembolism, recurrence, metastasis and survival should be followed.
• Interaction studies: Use with chemotherapy, immunotherapy, endocrine therapy, antiplatelet drugs and anticoagulants should be investigated.
• Benefit–harm balance: In a patient with sarcopenia, is the potential functional gain greater than any oncological risk?

The most valuable future study will not simply retrospectively compare patients "taking and not taking creatine". Supplement dose, exercise, muscle mass, tumor stage, platelet phenotype and treatments should be recorded together. Creatine may provide functional benefit in one person while producing different outcomes in another biological context.

Frequently asked questions

Conclusion: neither panic nor indifference is needed

The headline for this research is easy: "Creatine increased metastasis." The scientific meaning is more nuanced. With convincing mechanistic coherence, the study showed that external high-dose creatine could activate the CKB-STAT5B pathway in megakaryocytes to produce hyperactive platelets and that these platelets could facilitate tumor cell spread in mice.

However, the human data come from an uncontrolled, high-dose biomarker study lasting 14 days in 11 healthy young people. Cancer, recurrence, metastasis or life expectancy were not measured in humans. Therefore, the research is not evidence that creatine causes cancer; at the same time, it is a warning that casual use in cancer patients cannot be considered entirely risk-free.